Ventilating system washer cleaning apparatus

ABSTRACT

An apparatus for clearing ventilating systems of grease vapors, odors, smoke and the like which comprises a housing having inlet and outlet passages and enclosing between these passages, sequentially in the direction of air flow, a centrifugal extractor thereby substantially reversing the airstream flow, a continuous cold water spray intersecting and directed counter to the airstream flow and a group of electrostatic precipitators. The combined action of the extractor, water spray and precipitators remove variously sized grease, vapor and smoke particles from the ventilating airstream.

United States Patent King Sept. 23, 1975 [5 1 VENTILATING SYSTEM WASHER3,260,189 7/1966 Jensen 126/299 R NI APPARATUS 3,618,659 11/1971 Rawal165/1 3,628,311 12/1971 Costarella..... /228 X lnventorl Donald King,Luwsvflle. y- 3,660,045 5/1972 Gladu 23 277 c 3,672,126 6/1972 Goettle261/116 X [73] Assgnee' a" Kmg 3,702,756 11/1972 Bowman .1 /119 x3,731,462 5/1973 Costarella et a1... 98/115 K X 22] il d; July 12 19733,744,217 7/1973 Ebert 55/387 X 3,747,301 7/1973 Glover et al.. 55/104 X[21] App1.l 1o.:378,566 3,785,124 1/1974 Gaylord 55/118 3,788,041 1/1974Gaylord 55/129 [52] US. Cl. 55/122; 55/126; 55/139; O G TEN S OR A PLICTION 55/242; 55/260; SS/ G. 36; 913/ 15 K 1,019,617 2/1966 UnitedKingdom 55/126 [51] Int. C1. B03C 13/01 1,071,680 3/1954 France 55/122[58] Field of Search 126/299 R, 299 A, 299 B, 354,917 7/1961 Switzerland98/115 K 126/299 C, 300', 301; 98/115 R, K; 55/108, 110, 111, 118, 122,126, DIG. 36, Primary Examiner-Bernard Nozick 220, 239, 257, 259, 260,242, 481, 139; Attorney, Agent, or Firm-Woodard, Weikart,

261/126,115,116,1l7,l18 Emhardt& Naughton [56] References Cited [57]ABSTRACT UNITED STATES PATENTS An apparatus for clearing ventilatingsystems of grease 1,078,927 11/1913 Keltner 261/126 UX vapors, dors,smoke and the like which comprises a 111021996 7/1914 30116115161"261/126 UX housing having inlet and outlet passages and enclosinggerhold 1 between these passages, sequentially in the direction egg2,245,516 6/1941 Wintermute 55/122 x $5,?" a i frii 222; gzgfi gzg zi2,273,194 2/1942 Hedberg et a1. v.55/13 y reversllg e ea 2,347,7095/1944 Penney 55/118 Water Spray ""ersectmg and dlrected i F 2,387,34510/1945 Peary v I I 261/126 airstream flow and a group of electrostatlcprec1p1ta- 2,392,038 1/1946 Gaylord 55 010. 36 ms The m n d a ti n f thextra tor, water 2,555,216 5/1951 Wintermute 55/1 18 spray andprecipitators remove variously sized grease, 2,643,105 6/1953 Lipowitz261/126 X vapor and smoke particles from the ventilating air- 2,709,5805/1955 Kameya..... 261/111 Stream, 2,862,354 12/1958 Barnhart.... 55/1223,156,547 11/1964 Fleck 55/118 x 2 CIaImS, 6 Drawlng Flgures $54 2%54 5143 34 34 W47 a l 1' |5\ ','"7""" M 13 33 1 32 111/ we xxnwmen 24 2s \I,17 E 27b I 22 l 1 l Z1 US Patent Sept. 23,1975 Sheet 10M 3,907,525

US Patent Sept. 23,1975 Sheet 2 of4 3,907,525

Fig.3

US Patent Sept. 23,1975 Sheet 3 of4 3,907,525

VENTILATING SYSTEM WASHER CLEANING APPARATUS BACKGROUND OF THE INVENTIONThe ventilation of enclosures in which a smoke and grease ladenatmosphere is generated (for example, commercial and institutionalkitchens) is beset with problems. More generally, industrialinstallations also have difficulty with respect to, for example, removalof oil mist from the area adjacent to lathes and screw machines, removalof welding dust from in-plant welding shops, and removal of dust lintand vapors from various industrial processes. Difficulties in disposingof grease vapor, odors and smoke, time consuming clean-up andmaintenance of the equipment and ventilating apparams, the fire hazardresulting if such periodic clean-up is not rigorous are some of thedifficulties involved. Airpollution ordinances have foreclosed thepossibility of meeting these difficulties by merely dumping thecontaminated ventilating airstream to atmosphere exte rior of thebuilding or enclosure.

While use of electrostatic precipitators has, in the past, beenattempted in dust, oil and grease vapor laden enclosure ventilation, theresults have not been satisfactory because accumulation of grease on andadjacent the cells progressively inhibited their functioning. Theappratus of the present invention succeeds in meeting the ventilationproblem discussed above because it combines a cold water spray and awatercooled centrifugal extractor with the use of the electrostaticprecipitators. The centrifugal extractor and cold water curtain,directed generally counter to the flow of the ventilating airstream,serve to remove and wash away heavier grease vapors and the larger ofthe smoke particles. Since these are removed prior to entry of theairstream into the precipitator cell area, the cells can perform,without pregressive inhibition of their function, removal of the finalsmaller particles remaining in the airstream.

BRIEF DESCRIPTION OF THE DRAWINGS nozzles and their manifold.

FIG. 5 is a schematic view of the piping arrangement for the continuouscold water spray nozzle array shown in FIG. 4.

FIG. 6 is a schematic illustration of the piping arrangement for thewash-down nozzle array.

FIG. 7 is a schematic showing of the electrical circuit for theapparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1the apparatus of the present invention is shown generally at 10 and isformed by a tubular housing, the upper end of which is formed to providean outlet collar 1 l on which is mounted a motor drivenfan 12 enclosedin a suitable housing 13. The fan 12 and the housing protecting it maybeof any suitable type drawing air through the housing 10 and dischargingit in any suitable fashion either peripherally around the housing 13 orover the open upper end of the housing. It will be understood that thefan structure and the housing 13 form no part of the present inventionbut merely illustrate the environment in which the apparatus of thepresent invention, enclosed by the housing 14, is utilized. The fan 12merely serves to initiate the flow of ventilating air through thehousing 14 which is shown in detail in FIGS. 2 and 3.

Referring particularly to FIG. 2, the housing 14 is shown as generallyrectangular and tubular in configuration, one sidewall of the housingbeing formed by an access door 16. The access door is removable bymoving the door latch member 17 out of overlying relation to the upperedge of the access door and then sliding the access door upwardly out ofitss peripheral retaining members 17 formed integrally with the housingsidewall indicated at 18.

At its lower end the housing 14 carries an inlet collar 21 which isadapted to be installed on, for example, an existing roof-top duct exit,the apparatus and housing 14 thus being interposed between the roof-topduct exit and the conventional roof-top fan assembly which may beaccommodated on the outlet collar 11. The housing, adjacent the collar21, is provided with an inwardly turned flange 22 which thus forms aninlet passage for the airstram entering through the collar 21 asindicated by the air flow arrows in FIG. 2. The upper margin of thecollar 22 carries brackets 23 which support a baffle or plate 24 havinga depending skirt 26 which extends toward the collar and to a pointgenerally aligned with the upper margin of the inlet passage formed bythe collar 22. The inlet passage formed by collar 22 is smaller in crosssection than the housing which extends outwardly to its sidewalls andthus forms a peripheral trough within the housing indicated at 27 aswill be evident from the flow arrows of FIG. 2. The direction of flow ofthe airstream is substantially reversed by the skirt 26 of the baffle 24and the airstream moves toward the base of the trough 27 but is againdirected upwardly, by the trough, toward the outelet at the top of thehousing 14.

Above the baffle 24, the housing carries a support frame 31 which has adepending portion 31a forming an entry to the flat filter member 32which is supported on the frame 31. The filter 32 serves as a mist, ormoisture droplet barrier, and removes droplets from the airstream whichprogresses upwardly through the filter.

Supported on appropriate mounting members 33 is an array ofelectrostatic precipitator cells indicated generally at 34. Theseelectrostatic precipitator cells are well known in the prior art and areformed by collector plates 34a and include an ionizing section providedwith a relatively high DC voltage. Any particles remaining in theairstream as it passes upwardly through the cells move through theionizing section and are there given a positive charge. As these chargedparticles pass up into the collecting plate sections, they are attractedand held to the ground potential plates by a strong electrostatic field.As indicated by the arrows in FIG. 2 the airstream, after moving throughthe precipitator cells continues upwardly to exit through the outletcollar 1 1.

As may be seen in FIGS. 2 and 3, suitable brackets 36 carried on theexterior surface of the skirt 26 sup port a continuous, rectangularheader pipe 37 which is shown in detail in FIG. 4. A connecting tee 37aprovides for supply of cold water to the manifold 37. As may best beseen in FIG. 3, the tee 37a is connected to a supply pipe 38 which has abranch 40 extending to the exterior of the housing and to the extendingend of which a controlled, cold water supply pipe may be connected, thepiping connections being shown in detail in FIG. to be describedsubsequently. A capped alternate cold water inlet connection 39a isprovided for use as an alternate cold water inlet connection where thepiping must be brought to the assembly through the duct work on whichthe assembly is mounted. It will be understood that when the alternatesupply connection 39a is utilized, the supply connection 40 would becapped. Spaced around the length of the header 37 are continuous waterwash nozzles 39 which are of a conventional type and provide a spraypattern generally in the form illustrated in broken lines in FIG. 2. Itwill be noted that this cold water spray issuing from the nozzles 39 isdirected generally counter to the flow of ventilating air as it movesfrom the trough 27. Supported on the skirt 26 somewhat below the nozzles39 is generally rectangular configurated wash-down water manifold 41.Brackets 42 support the manifold and spaced along its length areoutwardly directed wash-down nozzles 43 which are of conventionalconstruction but which differ in spray pattern from the nozzles 39 inthat they direct peripherally outwardly a conical water spray ofapproximately 120 degrees. This wash-down water, supplied at intervalsas will subsequently be described, moves down the inner surface of thehousing sidewalls and into the trough 27 from whence it, together withthe water resulting from the spray issuing from the nozzles 39, drainsfrom the trough 27 through the drain connection 27a (FIG. 3). The greaseand particle laden drain water may be passed through a suitable greaseremoval unit (not shown) before discharge into the conventional drainagesystem. As may best be seen in FIG. 2, the wash-down water to the header41 is supplied by a pipe 46 and a portion 46a of this pipe extends tothe exterior of the housing and permits connection of a controlledsupply of hot water to be described in detail with reference to FIG. 6.The capped extension 46b of the pipe permits an alternate supplyconnection through the duct work.

As may best be seen in FIGS. 2 and 3 an array of hot water, wash-downnozzles 51 is supported in overlying relation to the precipitator cells,the nozzles being supplied by the header 52 which is connected to thedownwardly extending pipe 53 (FIG. 2) which joins the pipe 46 at thetee-connection 54. Adjacent the nozzles 51 are nozzles 54, adapted fordispensing a detergent solution into the area above the precipitatorcells for bathing the cells in the detergent solution at controlledintervals. Nozzles 54 are supplied by a separate header pipe adjacentthe header pipe supplying the nozzles 51 and this detergent supplyheader is connected to the pipe 56 (FIG. 3) which has a portion 56aextending to the exterior of the housing and which is adapted to besupplied with a detergent solution. An extending portion 56b, showncapped in FIG. 3, provides an alternate connection for supplyingdetergent to the pipe 56 and the nozzles 54. An alternate connection forthe trough 27, to be used where the drain piping must be brought throughthe duct work on which the apparatus is installed, is indicated at 27bin FIG. 3, this drain being capped when the drain connection 27a isutilized.

Referring to FIG. 5, the control connections for the continuous spraynozzles 39 will now be described. The union 62 is connected to the coldwater supply source and a manual stop valve 63, together with a vacuumbreaker 64 are provided. The solenoid valve 66 controls the flow of coldwater (a by-pass line 67 controlled by a manual valve 68 is alsoprovided) the manual valve 68 normally being closed during operation.The cold water supply line includes a line strainer 69, a pressureregulator 71 and a pressure gage 72. The downstream end 73 of the coldwater line is connected to the cold water nozzle line 39 (FIG. 3) whichsupplies water through the pipe 38 to the nozzles 37a. A branch line 74to the drain may be suppled and is controlled by the normally opensolenoid valve 76. The line 74 and the solenoid valve 76, when presentin the system, provide a means for automatically bleeding the supply andnozzle lines when the system is shut-off, thus preventing these linesfrom freezing in climates where this precaution is necessary.

Referring to FIG. 6, the piping arrangement for supplying hot water tothe nozzles 43 and 51, and detergent solution to the nozzles 54, willnow be described. The piping system for supplying hot water to the line77 which is connected to the line 46a (FIG. 3) includes a union 78 whichis connected to a source of hot water supply, a stop valve 79, a vacuumbreaker 81 and a normally closed solenoid valve 82. A by-pass includingthe manual stop valve 83 is provided around the solenoid valve, thevalve 83 being closed during normal operation of the apparatus. Anormally open solenoid valve 84 in the line 86 to the drain provides anarrangement for bleeding the line where temperatures require precautionagainst freezing. The detergent supply line 87 is connected to the line56a (FIG. 3) and extends to a detergent solution container 88, flow fromwhich through the line 87 is established by the electrically energizeddetergent pump 89. The control system for the apparatus is shownschematically in FIG. 7. It includes the power line members 101 and 102and a start-stop, push-button switch 103 which has normally open stopcontacts 103a and normally closed stop contacts 1031; connected inseries with the control relay CR-l Series connected contacts 103C and103d are connected in series with a pair of contacts identified at T-2Aand to the control relay identified at CR-2. Contacts T-2A arecontrolled by the timer motor T-2. Once timer motor T-2 has beenenergized, the contacts T-2A are not reclosed until a time delaysubsequent to de-energization of the timer T-2. The timer T-l isenergized with relay control CR-2 and the detergent pump 89 is connectedto this circuit through the normally closed timer actuated switch T-IA.The contacts T-lA are opened by the timer T-l after a short time periodof the order of 15 seconds so that detergent solution is supplied to thenozzles 54 only for this short period during the washdown cycle. Thestart-stop switch 103 is provided with holding contacts CR-lA and CR-2Awhich are closed by the energization of the relay coils CR-l and CR-Z,respectively. Connected between the upper one of the contacts CR-2A andthe supply line 102 is a control relay identified as CR-3 which has inseries with it a the airstream. The thermostat 106 is not shown in FIGS.2 and 3, however, it will be understood that it functions as areverse-acting high temperature limit control and is appropriatelylocated in the duct work through which the ventilating airstream passesas it moves to the apparatus of the present invention. The timer T-2 isconnected across the lines 101 and 102 through the parallel connectedcontrol relay switch identified at CR'2B and timer controlled switchT-2B, energization of the control relay CR-2 closing the switch CR-ZBand the switch T-2B being closed by the timer T-2. A wash cycleindicator light may be provided in parallel with the timer T-2.

The hot water solenoid valve 82, mentioned previously, is connectedacross the power lines 101 and 102 by means of the parallel connectedswitches CR-3B and T-2D. The switch CR-3B is closed upon energization ofthe relay CR-3 and the switch T-2D is closed by the timer switch T-2after a delay period of approximately 5 minutes subsequent toenergization of the timer T-2.

A normally closed relay switch identified as CR-3C, and opened uponenergization of the control relay CR-3, is connected in series with anormally open pair of contacts identified as CR-lB, these contacts beingclosed upon energization of control relay CR-l. These series connectedrelay switches have connected to them a circuit branch identified at 108which connects to the parallel connected members 12a, 12b and cold watersolenoid valve 66. The exhaust fan control coil is identified by 12a,and, it will be understood, that energization of the member 12a causesclosing or comple tion of the electrical power circuit to the drivingmotor of the ventilating fan 12 (FIG. 3). The control member 12brepresents the energizing coil for a control switch which energizes theelectrical motor driving a make-up air fan which, in some applications,is located in the duct leading to the enclosure (kitchen) from theoutside. The makeup air fan is not shown (other than its controller 121;of FIG. 7) since its presence is optional and is not included in allinstallations. The solenoid valve 66 is, of course, the cold watersolenoid valve shown in FIG. 5, and controls the flow of cold water tothe nozzles 39 (FIG. 2).

Connected in parallel to the circuit branch 108 is a wire 109 whichserves to connect the power pack 110 to the power input. In series withthe power pack 110 are normally closed timer switch T-2C and thenormally closed door switch 111. The door switch 111 is shown in FIG. 2and is mechanically closed by the presence of the access door 15. Whenthe access door 16 is opened or removed from the bracket 17, the doorswitch 111 is opened, the switch thus functioning as a safety switchpermitting energization of the power pack 110 only when the door 16 isin place. The power pack 110 is primarily a step-up transformer and arectifier which supply the elevated, DC voltage necessary to provide theionizing charge to the precipitator plates 34a. The switch T-2C isopened upon starting of the wash cycle, that is, when the timer T-2 isenergized and is returned to closed position only after a time intervalof the order of 30 minutes has elapsed subsequent to the termination ofthe wash cycle to provide against the precipitator cells being energizedbefore they have dryed subsequent to the wash cycle.

In operation, to start the system, the start button of the switch 103 isdepressed therby energizing control relay CR-l. This causesenergization, through the switch CR-lB and wire 108, of the exhaust fan12, the make-up air fan 12b, if such is used, and energizes the coldwater solenoid valve 66 providing a cold water spray from the nozzles 39(FIG. 2). Assuming the accessdoor 16 is in place, the power pack and theprecipitator cells are also energized through the relay contacts CR-lB.Operation may now continue as desired and when the apparatus is to bede-energized, the stop button of the switch 103 is depressed.Deenergization of control relay CR-l, through opening of the relaycontacts CR-lB thereupon de-energizes the fan controls 12a and 12b andcloses the cold water solenoid valve 66 and de-energizes the power pack110. Depression of the stop-button of the switch 103 causes controlrelay CR-2 to be energized through the contacts 103: and contacts 103!)of the switch 103. Energization of relay CR-2 closes relay contactsCR-2B and energizes timer T-2. Timer T-l is also energized as is thedetergent solution pump 89 so that detergent solution is sprayed fromthe nozzles 54 (FIG. 2) for a timer interval until time T-1 opens thecontacts T-lA, the time interval being of the order of 15 seconds. Because the timer T-2 closes the contacts T-2D only after a time delay,subsequent to its energization, of approximately 5 minutes, thedetergent solution sprayed from the nozzles 54 onto the precipitatorcells is permitted to soak until the 5 minute delay interval timed bythe timer T-2 has been completed and switch T-2D is closed, therebyopening the hot water solenoid valve 82 which supplies rinsing hot waterspray to the nozzles 5 1 and the nozzles 43 (FIG. 2). This rinse orwash-down cycle is completed at the end of the predetermined timeinterval by opening of the timer contacts T-2D by the timer T-2. Thetimer motor T-2 retains the timer contacts T-2C open for the 30 to 40minute interval necessary to assure that the precipitator cells havedryed. After this time period passes, the timer T2 opens the contactsT-2A, de-energizing the timer and the wash cycle light. Operation of theapparatus may then be restarted by again depressing the start button ofthe switch 103. It should also be noted that operation of the exhaustfan 12 (energized by controller 12a) and the continuous water washcontrolled by solenoid valve 66, and issuing from nozzles 39, can bereinstituted without waiting for the lapse of the time intervalnecessary for reclosure of timer switch T-2C and reenergizationelectrostatic precipitator power pack 110. Depressing the start buttonof switch 103 immediately after release of the stop button deenergizesrelay CR-3, closing switch Cr-3C, and energizes relay CR-l, closingswitch CR'IB. The exhaust fan 12 and the cold water spray (controlled bysolenoid valve 66) are thus restarted immediately. This mode ofoperation is utilized where the process being ventilated cannot be shutdown for any extended period of time. As the circuit of FIG. 7indicates, the system can be stopped without automatically going intothe wash-down cycle by depres sion of both the start and stop buttons ofthe switch 103 simultaneously.

When both buttons are depressed simultaneously control relay CR-2 is notenergized and timer T-2 is not started and the wash-down cycle does notoccur.

It should be noted that a safety feature is provided in that the ductthermostat 106 overrides all other controls in the circuit to startwater flow from the washdown nozzles 43 and 51 upon the existance of anabnormally high temperature in the air flow duct. With the system inoperation and the switch 103 in released or quiescent condition, closureof duct thermostat 106 energizes control relay CR-3, which closes relayswitch CR-3B energizing solenoid valve 82 and causing washmight also beinstalled in horizontal position with the plate 20 lowermost.

I claim:

1. Apparatus for clearing grease vapors, odors,

down nozzles to spray water until the start button of smoke and the likefrom enclosure ventilating systems switch 103 is manually depressed. lfthermostat 106 remains closed, indicating the abnormal duct temperaturepersists, the flow of wash-down water will immediately start again whenthe start button is released, and the system cannot be reset by thestart button until after the duct thermostat 106 has opened itscontacts.

Referring again to FIG. 3, it will be noted that one side of the housing14 is provided with a drain panel to permit water from the prccipitatorcell area to drain back to the drainage area provided by drainconnection 27a when the apparatus is installed horizontally, rather thanvertically as shown in FlGS. 2 and 3.

From the foregoing it will be evident that the apparatus of the presentinvention combines three elements to clean grease vapors, odors andsmoke from ventilating systems. These combined elements are the watercooled centrifugal extractor formed by the trough 27 and baffle skirt 26which causes a reversal in the airstream flow depositing the heavierparticles entrained in the airstream at the base of the trough 27. Thecontinuous water washing of the airstream, flowing counter to the waterspray, provided by the nozzles 39 tends to remove remaining greasevapors and larger greasy smoke particles from the airstream. Theelectrostatic precipitator component takes out the remaining smallparticles in the airstream. Since the larger particles are eliminatedfrom the airstream before it reaches the precipitator cells, theseoperate with maximum efficiency.

As pointed out above, to facilitate cleaning and maintenance of theapparatus, a wash-down program is incorporated in the apparatus toautomatically wash the electrostatic cells and the spray chamber ortrough with hot water and detergent when the unit is shut-down. Thebaffle 24 with its depending skirt 26, forming a part of the centrifugalextractor, can be removed for periodic complete cleaning and access tothe nozzles. Access to the filter 32 and the precipitator cells can beobtained, as previously mentioned, through the access door. While theunit has been shown installed vertically on a roof-top for example, itwill be understood that it having a power induced ventilating airstreamdischarged through an outlet mouth exterior of the enclosure, saidapparatus comprising a generally tubular housing having one endproviding an inlet passage and adapted to overlie and register with theoutlet mouth of the ventilating system, the opposite end of said housingproviding an outlet passage through which the cleansed ventilatingairstream exits, said inlet and outlet passages being substantially inaxial alignment, said housing having an inwardly turned flange at saidinlet end completely encircling said inlet passage in the housing, saidinlet passage being substantially smaller in cross section than thehousing interior so that the housing sidewall and flange form a troughsurrounding said inlet passage, a baffle plate overlying but spaced fromsaid inwardly turned flange and having a peripheral skirt extendingtoward said trough whereby the direction of flow of said airstream isreversed and then redirected again toward the housing outlet as it flowsaround said skirt and out of said trough, electrostatic precipitatorcells supported within said housing and disposed in said airstreamdownstream of said trough, and an array of nozzles supported on thedownstream side of said baffle plate, said nozzles being positioned inspaced relation around the margin of the baffle plate and protrudingslightly beyond said plate margin to deliver an axially directed sprayof cold water in the annular space between the peripheral wall of thehousing and said baffle skirt which intersects and flows substantiallycounter to the airstream as it flows between said skirt and said housingperipheral wall and prior to its movement past said precipitator cells.

2. Apparatus as claimed in claim 1 in which a further array of nozzles(43) encircles said baffle plate and is supported on said peripheralskirt of the baffle plate, said further nozzle array being disposedcloser to the base of said trough than said first mentioned array ofnozzles and adapted to deliver wash-down water to said trough.

1. APPARATUS FOR CLEARING GREAS VAPORS, ODORS, SMOKE AND THE LIKE FROMENCLOSURE VENTILATING SYSTEMS HAVING A POWER INDUCED VENTILATINGAIRSTREAM DISCHARGED THROUGH AN OUTLET MOUTH EXTERIOR OF THE ENCLOSURE,SAID APPARATUS COMPRISING A GENERALLY TUBULAR HOUSING HAVING ONE ENDPROVIDING AN INLET PASSAGE AND ADAPTED TO OVERTILE AND REGISTER WITH THEOUTLET MOUTH OF THE VENTILATING SYSTEM, THE OPPOSITE END OF SAID HOUSINGPROVIDING AN OUTLET PASSAGE THROUGH WHICH THE CLEANSED VENTILATINGAIRSTREAM EXITS, SAID INLET AND OUTLET PASSAGES BEING SUBSTANTIALLY INAXIAL ALIGMENT, SAID HOUSING HAVING AN INWARDLY TURNED FLANGE AT SAIDINLET END COMPLETELY ENCIRCULING SAID INLET PASSAGE IN THE HOUSING, SAIDINLET PASSAGE BEING SUBSTANTIALLY SMALLER IN CROSS SECTION THAN THEHOUSING INTERIOR SO THAT THE HOUSING SIDEWALL AND FLANGE FROM A TROUGHSURROUNDING SAID INLET PASSAGE, A BAFFLE PLATE OVERYLING BUT SPACED FROMSAID INWARDLY TURNED FLANGE AND HAVING A PERIPHERAL SKIRT EXTENDINGTOWARD SAID TROUGH WHEREBY THE DIRECTION OF FLOW OF SAID AIRSTREAM INREVERSED AND THEN REDIRECTED AGAIN TOWARD THE HOUSING OUTLET AS IT FLOWSAROUND SAID SKIRT AND OUT OF SAID TROUGH, ELECTROSTATIC PRECIPTATORCELLS SUPPORTED WITHIN SAID HOUSING AND DISPOSED IN SAID AIRSTREAMDOWNSTREAM OF SAID TROUGH, AND AN ARRAY OF NOZZLES SUPPORTED ON THEDOWN-
 2. Apparatus as claimed in claim 1 in which a further array ofnozzles (43) encircles said baffle plate and is supported on saidperipheral skirt of the baffle plate, said further nozzle array beingdisposed closer to the base of said trough than said first mentionedarray of nozzles and adapted to deliver wash-down water to said trough.